Process and apparatus for preconditioning cooking solutions



N0v. -17, 19,31. T, DUNBAR 1,832,367

PROCESS AND APPARATUS FOR PRECONDITIONING COOKING SOLUTIONS NV. 17,1931. T, j DUNBAR 1,832,367

PROCESS AND APPARATUS FOR PRECONDITIONING COOKING SOLUTIONS Filed May17, 1930 a' sheets-sheet 2 Dgeser Swim/nto@ T. L Dunbar,

ccumu Zaior A PROCESS AND APPARATUS FOR PRECONDITIONING COOKINGSOLUTIONS Filed May 17. 1930 3 Sheets-Sheet 3 Patented. Nov. 17, 1931UNITED l srxrlas` THoMns L. DUNBAB, or WATERTWN, NEW YORK PATENT oFF-ICEPROCESS ANDL APPARATUS FOR PRECONDITIONING COOKING vSOLUTION-SApplication iled May 17,

of heat and the recovery of SO2 or other gases, y

in the digestion of fibrous material for pulp making purposes. 7 Inaccordance With the invention, improved means are employed to save heatunits, by 10 transferring the same from liquor Which is relieved fromcooking vessels or digesters previous to the discharge of the main bodyo f pulp therefrom, to cold fresh cooking solution or acid liquor, bytheuse oficonventional heat exchange means, While concurrently andseparately mixing gases relieved from the digesters With fresh cookingsolution Within a closed vessel or system, thereby recovering the heatunits as Well as the gases. f) In some existing processes, both thegases and liquids relieved from a digester are passed into anotherdigester, and in the latter, they are mixed with the new charge of raw.vegetable matter and cookingjsolution. In if other processes, both`lthe relief .gases and liquids are passed into a body of'fresh cookingsolution under pressure, and the last mentioned solution' is usuallycontained. in a closed vessel, commonly called an accumulator. For

' 33 certain purposes, it is undesirable to so mix' the relieved liquidportion directly with the fresh cooking solution, or to mix it with aneW charge of vegetable matter to be cooked.

` To meet such a contingency, I have invented an improved process` andapparatus, and in accordance With the invention, I provide means tosepa-rate the relieved liquid Afrom the relieve-d gas, and then utilizeheat units derived from the liquid portion of the yrelieved mixture topreheat aI portion of the,'fresh cold f relief liquid is cooled down tothe point Where i it can advantageously be employed, I cause the gaseousportion Which has been separated "n from the relieved mixture, to beabsorbed, by

tion at a period ink its preparation, when it 1930. semi No. 453,256.

introducing said gaseous portion directly into fresh cooking solutiorfin a separate vessel, in which the gas is absorbed under super#atmospheric pressure.

A further object ofthe invention is to relieve gases andliquids from adigester, and

to separate the relieved mixture into liquid and gaseous fractions; theliquid fraction or fractions being employed to indirectly heat freshacid liquor, and the latter being ern-60 p loyed to absorb the gaseousfraction or fractions.

With the foregoingn objects outlined and With other objects in viewwhich will appear as the description proceeds, the invention consists inthe novel features hereinafter described in detail, villustrated in the.accompanying drawings', and more particularly pointed out in theappended] claims.

vfInthe drawings,

Figs. 1, 2 and 3 are sideelevations respectively of three embodiments ofnovel apparatus which I have invented for use in carrying out myimproved process.

, Referring first to Fig. l, it will be observed that 5 Ais a digester,11 a pfressure accumulator, 7 a combined heat exchanger and separator,16 a. separator, 22 aheat' exchanger,and 30 a recelver. i l

When practicing the process With the apparatus shown in Fig. l, chemicalgases, vapors-and liquids are relieved from the ltopfof a digester,vthrough the pipes 6, fromiwhich they flow into the separator 7. Verticaland horizontal baiiies 8 and 9 are arranged With- 85 inthe closedseparator to assist in separating the gaseous portionof therelievedmixture from the liquid portion thereof, and the gaseous portionthus separated passes olf by Way of the valved pipe 10, into the lowerportion ofthe laccumulator which contains fresh acid liquor. that isused to `absorb the as. f 1 g Heat unitsof the liquid portion of therelief mixture are transferred from the liquid in the separator, to the.heat exchange 'coil 36, through Which fresh/ chemical liquor passes onits Way tothe'accumulator, and after the liquid portion of the reliefmix-7 ture has been deprived-of heat units. in `this pipe 15. The valve14 is set to hold a pressure in the separator 7, so that the separationin this vessel takes place under pressure.

'uid,. this gas passing upward through thev The element 14 may be apressure actuated relief valve of any suitable form, for mamtaining apressure of a suitable magnitudex in pipes 13 and 12,-and in vessel 7,while allowing a ,lower orfsubstantially atmospheric pressure tobemaintained in the pipe 15 and separator 16, through which the reliefliquor may subsequently pass. Thus, the separator 16 acts asaflashchamber, wherein a portion of the absorbed gas releases fronr theliquid, owing to the reduction@ of pressure. 'Y The flash chamber ,ispreferably equipped with suitable baiing, means 17 to facilitate thefurther separation of gas from the relief liqpipe 18, from which it may(flow into a mixer 19, or from which it may entera valved pipe 20, whichmay lead the'same to atmosphere or to a part of the acid preparationplant,

in case it is desired to absorb this gas in cool acid at any earlierstage in the processv of acid preparation.

The liquid portion of the relief liquor from the separator 16, passes bymeans of pipe 21, into the casingy of the heat exchanger 22,

and from the latter, it is discharged through a pipe 23.

The cold acid liquor is fed from the mixer 19, through a pipe 24 that isconnected to a coil 25 arranged within the heat exchanger.

Of course, this coil is of suitable heat conducting material, so ythatthe fresh acid liquor is somewhat heated by the relief liquid dow"- ingthrough the casing 22.' The fresh liquor thus preheated, passes -by wayof a pipe 26 to the coil 36, and froim the latter,the now more highlyheated liquor -iows through a pipe 37, into the accumulator 11, whereinit acts to absorb the gaseous fractionof the re# lief liquid-whichenters by way of pipe 10.

The cooled relief liquor leaving through the pipe 23, may. be divertedto waste, through valved pipe 27, or may be returned to the liquorpreparation plant through pipe 28, or it may be conducted through avalve pipe 29 to a storage vessel 30, from which it may be drawn asdesired through valved pipe 31. The vessel 30 is preferably providedwith an overflow pipe 32 for passing excess liquor I, to waste. 1

.lieved liquor from the vessels 7 and 22 imparts its heat unitsindirectly to the fresh `cooking solution, while the latter is on itsaccumulator, While the remainder may flow through the `pipe 18 to bemixed in 19 with fresh cookingsolution at the time the latter enters myapparatus. Y

In the embodiment of the invention shown in Fig. 2, the process isl inall essentials similar to that described in connection with Fig. 1,'lbut the apparatus is of somewhat simpler construction. In thisform ofthe apparatus, 40 designates a digester having valved relief pipes 41leading into `a separator and heat exchanger 42. From thisclosedseparator, which also has internalbaiiles, the relief gas passesby way'of pipe 51, into the cooking solution in the accumulator.`

In this arrangement, the difference lies in combining in one vessel 43,the functions of the parts 16, 22 and 30 of Fig. 1, with their dependentaccessories. Thus, vessel 43 serves as a storage tank for separatedrelief liquor under a lower pressure than exists in the separator 42,due to the use of the pressure operated valve 143 which is interposed inthe pipe line 144, leading from 42 to 43. Vessel 43 also acts as asecondary separator or flash chamber` having suitable internal bafflingmeans 44 to aid the separation of gas from .the liquid. Furthermore, thevessel 43 and the coil 44 arranged therein, functions as a heatexchanger corresponding to the first heat exchanger-'in Fig. 1.

In this form of the invention, the fresh cqoking solution enters' theapparatus through the pipe 49, .from which it flows into a mixer 46. Thelatter is placed in a rising extension 146 of the vessel 43, so that gasseparated from the relief mixture in said vessel, will flow upwardly andinto the mixer to be thoroughly commingled' with the' fresh cookingsolution, and to be absorbed thereby as the latter flows on and into theheat exchange vcoil 45. TheJ outlet of this coil is joined by a pipe 147,to avhe'at exchanging coil 148, positioned in the tank 42, and theoutlet from this coil is connected by a pipe 149 to the accumulator. I

TheL vessel 43 has avalved discharge line for leadin relief liquoreither to waste, or to the coo ing solution preparation plant, andatrapped overflow pipe 47 for the vessel 43 prevents the completefilling of thetank with liquid, thus insuring suicient space within theupper portion of the tank for the separation of the gas fromthe liquid.

For the purpose of agitating the liquid in the vessel 43 tofacilitatefheat exchange and the freeingl of absorbed gases, the vessel43i may have an agitator 5.0, driven by any suitable means from theexterior of the vessel'.

Maase? l In the modification illustrated in Fi 3, the gases, vapors andliquids resultingv rom the cooking in the digester 52, are dischargedthrough the valved branches 53, into a conduit 54 that conducts the sameinto the top of a pressure separator 55 which contains any suitablebaffling means 56 to assist in the septure, are discharged from the topof the vessel 55, by way of the pipe 60 which leads to a mixer 74.

The liquid fraction fromthe separator fiows through a U-shaped trap pipehaving arms 61 and 62, into a pressure operated valve 63 which functionsto maintain the separator 55 Linder super-atmospheric pressure.

From the valve, the liquid flows through a conduit 64, into a Hashseparator 65, and from the latter, the `liquid fraction ,is Vdischargedthrough a pipe 66 'having al trap portion 67. The liquid leaving thepipe 66 may be conducted to waste, or may be lreturned to the `cookingsolution preparation system.

The vessel 65 is under a lower pressure'than the vessel 55, so thatgasesyare evolved-in the sparator 65, and these gases pass upwardthrough a pipe 68 to a suitable height, and

thence are led by a pipe 69 into a gas mixer 70, through which the coldcooking` solution .is pumped on its wayto the accumulator 73. `In themixer, the gas is absorbed by the fresh cold cooking solution enteringeither from storage or directly from the preparation plant. The mixedsolutionfrom mixer 70 flows by way of pipe 71, into 'the coil 57, and asit flows through thelatter, it is' heated by the hot relief liquidin'the've'ssel 55, and

from the coil, the substantially fresh preheat ed cookingnsolution flowsthrough a conduit 72, into the mixer 74, where it meets the hot gasesfrom the pipe 60. These gases act vto further heat the :cookingsolution, and the latter functions to absorb these gases, and the fcombined mixture flows from the mixer` through a discharge pipe 75 thatleads to a cumuIatOr. f

, I desire to be understood that while I have illustrated only onedigester for each embodiment of the invention, that any number ofdigesters may be employed with my inven tion, and that such digesters,lasy well as the accumulators, are maintained under superatmosphericpressure. L

It will also be understood that the fresh cooking solution,preconditioned and pre- 'i heated in accordance with the invention, 1s

vto be fed from the accumulator to any one ofgaseous portion, so thatthe liquid portion does not directly enter the new cooking solution,-and yet, the latter extractsheat units from the liquid portionof'therelief, by means of the heat exchanger or heat exchangers, whichprevents the commingling of the two liquids. Furthermore, by the use ofheat ex changers, the liquid fraction or fractions of the relief mixtureis made relatively cool before admixing the same with the fresh cook#ing solution, and before the latter enters the pressure accumulator.A

By arranging a deep hydrostatic sealing leg or U tube on the kexit sideof the pressure separator, and locating apressure actuated relief valveposterior to the'vU tube, I obtain the following result. Assuming thatthe relief valve 14 (143, 63), is set to pop at 25 lbs. gauge pressure,and thevertical distance from the bottom of thel U tube to the level ofthe liquid in the pressure separator is 46 feet (equivalent to a staticpressure of approximately 20 lbs), then the valve 14 will allow theescape of liquid at v 25 lbs. pressure, if the lief valve 14 lmay besituated) When, howf ever, thel pressure in the separator 7, forexample, is in excess of 25 lbs., the valve will still pass liquidwi-thout passing gas, as the liquid will lower in the descending leg 12,

-and the pressure separator 7 will remainV sealed until a pressure of 45lbs. is reached therein. Thus, it may beseen that the use of thehydraulic leg or seal, avoids the necessity of precision in thelsettingofthe relief valve 14, for'instargze, and permits a wide variation inpressure-within the separator 7, without allowing gas to escape throughAthe relief valve 14. I

While II have disclosed what I now consider to be preferred embodimentsof the invention in such manner that the same may bereadily understoodby those skilledin the art, I ,am aware that changes may be made in thedetails disclosed, without departing from the spirit of the invention,as expressed in the claims. t

What I claim ters Patent is: i Y 1. In the digestion` of fibrousmaterial, re-

and desire to secure by Letleasing relief Huid from a digester during a1 cooking operation, separating the relief fluid into a gaseous fractionand a liquid fraction,Y `the chamber into a gaseous fraction and a andflowing relatively cold fresh cookingso lution in heat exchange relationwith the liquid fraction while maintaining "such fresh cooking solutionvout of contact with the liquid fraction. y

2. In the digestion of fibrous material, releasing relief fluid from adigester during a cooking operation, separating the relief fiuid into'agaseous fraction and a liquid fraction, passing relatively cold freshcooking solution through the liquid fraction whilemainv indirect heatexchange while the liquid frac-- tion is in said chamber and tainingsuch fresh cooking solution out of contact with the liquid fraction, andcommingling the gaseous fraction with the fresh cooking solution afterthe latter has been passed through the liquid fraction. d

3. In the digestion of fibrous material, releasing-relief fiuid from yadigester during a cooking operation, separating the relief fluid into agaseous fraction and a liquid/fraction, passing relatively cold freshcooking. solution through the liquid fraction while maintaining suchfresh cooking solution out of contact with the liquid fraction, feedingthe fresh cooking solution after passing through the liquid fraction,into a pressure accumulator,

and mixing the gaseous fraction with the fresh cooking solution afterthe latter` has passed through the liquid fraction. y

4. In the difgestion of fibrous material, releasing relief `uid" from adigester during the cooking period, and introducing the same intoapressure chamber wherethe liquid fraction of the relief mixtureseparates from7 the gaseous fraction thereof, and passing fresh cooking`solution vthrough the liquid fraction by while it is still hot. y

5. A processas claimed in claim 4, in which the gaseous fraction fromthepressure chamber, While still hot, is introduced into the freshd cookingsolution after the latter has passed through the liquid fraction.

6. A process as claimed in claim 4, m which the fresh cooking solution,after passing through the liquid fraction, is introduced into avpressure accumulator chamber, and commingling the` gaseous fractionwhile still hot, with the fresh cooking solution after the latter haspassed through the liquid fraction.`

7 A process as claimed in claim 4, ,in which the liquid fraction assesthrough 'the pressure chamber and't eny has its 'pressure released,whereby a secondary gaseous fraction is produced, and mixing thesecondary gaseouslfraction with the fresh cooking solution before thelatter has passed through the liquid fraction.

8. Int-he digestion of fibrous material, releasing fluid mixture from adigester during the cooking period, introducing the mixture into' aclosed pressure separator Vmaintained under pressure, ,separating saidmixture in liquid fraction, discharging a portion of the liquid fractionfrom said chamber, releasing the pressure on the relief fractiondischarged from the chamber, and introducing the same into a iashseparating means, feeding fresh cooking solution through a passagewaywhich i extends through the pressure separator and the flash separatingmeans, transferring heat units from the liquidffractionjto the freshcooking solution as it flows through said passageway, and mixingasecondary gaseous fraction of the relief mixture from the Hashseparating means with 4the cooking solution fiowiug through saidpassageway.

9. A process as claimed in'claim 8, in which the gaseous fractionffromthe pressure separator is introduced into `the fresh cooking solutionafter the latter has passed through said pressure separator.

'10. A process as claimed in claim 8, in which the liquid fraction inone of said separators is agitated 13o/facilitate heat exchan e with thefresh cooking solution flowing trough the passageway.

ll. A process of preheating and preconditioning cooking liquor to beused in the digestion of fibrous material, comprising discharging LeliefHuid from a digester into a separator chamber maintained undersupervatmospheric pressure, separating the relief Huid in said chamberinto a gaseous fraction and a liquid fraction, passing fresh cookinggolution through the liquid fraction while maintainingthe same out .ofcontact with said liquid fraction, and thereby transferring heat unitsfrom the liquid fraction to the' fresh cooking solution, discharging thegaseous fraction froml the separator chamber and introducing the sameinto the cooking solution after the latter has"passed through the liquidfraction, and thereby transferring heat units from the aseous fraction:to the cooking solution and' a orbing the gaseous fraction in thecooking solution, discharging the liquid fraction from theseparator`chamber through 'a hydraulic seal, and then releasing thepressure on the liquid fraction.

1.2. A process as claimed in claim" 11, in I which the released liquidfraction after its pressure has been reduced, is introduced into va Hashseparator, separating from the. liquid fraction in the Hash separator, asecondary gaseous fract1on,and mixing the secondary 'gaseous fractionwith the fresh cooking so- A lution before thelatter passes through theliquid fraction 'in the pressure separating chamber. I i

13. An apparatus of the character described, comprising a digester, anaccumula tor, a separator,"meansfor leading relief Huid from thedigester to the separator, a fresh cooking vsolution passageway leadingto the accumulator gud having a heat exchange portion arranged in theseparator,

iti

ranged in the separator, an accumulator, a

conduit leading from the outlet of the coil 4to the accumulator, meansfor introducing fresh cooking solution into the inlet of the coil, meansfor discharging a gaseous relief fraction from the separator andintroducing the same into fresh cooking solution after the latter haspassed through said coil, a trap pipe for discharging a liquid relieffraction from the separator, and a pressure operated valve connected tothe last menytioned pipe for maintaining pressure within the separator.

15. An apparatus of the character described, comprising a digester, aseparator, means for passing relief fluid from the digcster to theseparator, a heat exchange coil arranged in the separator, anaccumulator,

a conduit leading from the outlet of the coil to the accumulator, meansfor introducing fresh cooking solution into the inlet of the coil, meansfor discharging a gaseous relief fraction from the separator andintroducing the same into fresh cooking solution after the latter haspassed through said coil, a trapl pipe for discharging a liquid'relieffraction from the separator, and a pressure .operated valve connected tothe last mentioned pipe for maintaining pressure Within the lseparator,said Valve being arranged posterior to the trap in the pipe.

16. An apparatus of the character 'described, comprising a digester,means for discharging relief fluid from the digester, a separator intowhich saidmeans discharges, an accumulator, a fresh cooking solutionpassageway leading to the accumulator and having a heat exchange portionarranged scribed, comprising a digester, a pressure separator, means forleading relief fluid from the digester into the separator, a pres.V

sure accumulator, a fresh cooking solution passageway leading totheaccumulator and having a heat exchange portion arranged within theseparator, means for discharglng a gaseous relief fraction from theseparator land introducing the same into the fresh cooking solutionafter the latter has passed through the separator, a liquid relieffraction conduitl leading from the separator, a pressure operated valveAinterposed in said conduit for maintaining the separator-undersuper-atmospheric pressure, a flash-separator into which said conduitdischarges, means for feeding a gaseous relief fraction from the flashseparator into the cooking solution passageway anterior to the heatexchange portion of the same, and a second .heat exchange portion forsaid passageway heated by relief liquid of the fiash separator.

19. An apparatus of the character'dev scribed, comprising a digester, apressure separator, means for leading -relief fluid from the digesterinto the separator,-a pressure accumulator, a fresh cooking solutionpassageway leading to the accumulator and having a heat exchange portionarranged within the separator, means for discharging a vgaseousrelief-fraction from the separator and for introducing the same into thefresh cooking solution after the latter has passed through theseparator, a liquid relief fraction conduit leadin from the separator, apressure operated alve interposed in said conduit 'for maintaining these arator under super-atmospheric pressure, a ash separator into whichsaid conduit discharges, means for feeding a gaseous lrelief fractionfrom the flash separator into the cooking solution passageway anteriorto the heat exchange portion of the same, a second heat exchange portionfor said passageway heated by relief liquid of the flash separator, andan agitator arranged in one of said separators.4

In testimony whereof, I have hereto 4 affixed my signature. Y

THOMAS L. DUNBAR.

including means for leading the liquidfraction from said valve to aflash separator maintained vat substantially atmospheric pressure, andmeans forfeeding a gaseous relief fraction from the Hash separator intothe fresh acid solution passageway anterior to the heat exchange portionof theA same.

18, An apparatus of the character de-

